Lubricants Used in Centrifugal Slurry Pumps

Tobee^® utilises anti-friction rolling element slurry pump bearings. They may be either grease or oil lubricated. The advantages and disadvantages of each type are shown in below table.

Grease lubrication has been found to be the best choice for virtually all the applications of Tobee^® bearing assemblies (both horizontal and vertical types). The large population of Tobee grease lubricated slurry pumps is testimony to this fact.

Oil lubrication (ie the bearings dip into a bath of oil in the bottom of the oil bath lubrication) can offer improved operating performance for low temperatures or wide temperature ranges as well as higher speeds than grease. The primary reason for selecting oil for high speeds is that grease is flung off the bearing, which will cause metal to metal contact and subsequent failure.

ADVANTAGES	DISADVANTAGES
Grease • Proven experience. More than 5,000 Tobee slurry pumps operating worldwide lubricated with grease. • Grease and then plug off — regular re-greasing is normally not necessary between maintenance intervals • Good for dirty environments • Labyrinths and seals can be purged with grease that is compatible with the bearing grease • Applied in both horizontal and vertical slurry pumps • Bearings, once “run-in”, run cool and excess grease is automatically expelled by the bearing • High Temperature grease option • The bearings are always covered with a film of grease, preventing corrosion	Grease • Condition of grease cannot be monitored externally • Re-greasing can introduce contaminants, especially if grease nipples are not cleaned • Excess grease can cause churning and excess heating • Identification of grease is lost once loaded into a grease gun • Unsuitable for submerged bearing assembly applications • Contaminants can get churned into the grease • Lubrication cannot be externally cooled
Oil • Oil level and condition can be visually checked by means of a dipstick or sight glass (even while running) • More oil can be added or whole system drained and refilled without dismantling the bearing assembly • Operates over wider and lower temperature ranges than grease • Condition monitoring can be used to check oil and bearing condition • Oil can be cooled by passing through an external heat exchanger • Particle contamination can be removed by an external filtering system • Suitable for submerged bearing assembly applications • There are a wide selection of oil grades and synthetic	Oil • Tobee® adjustable bearing assembly design does not allow optimum airflow for heat dissipation • Sealing is critical. Leaked oil collects dirt. • Maintaining correct level is critical. Slurry Pump must be kept level to maintain correct oil level in both bearings. • Excess can lead to leaks, foaming and heating • Not suitable for vertical applications • A modified design of bearing housing is required with sump and dipstick • One level must suit both bearings in the assembly • Oil can run off bearings during long shutdown and leave bearings exposed to corrosion or boundary lubrication during start-up • Better suited to “clean” environments

Lubricants used in Centrifugal Slurry Pumps

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